1. Field of the Invention
This invention relates to apparatus for extracting particulate matter from an air stream, for example, extracting lint carried by the air stream flowing from a laundry dryer.
2. Description of the Prior Art
Many commercial operations, for example, saw mills, flour mills, furniture factories and commercial laundries have a stream of exhaust air carrying particulate matter such as sawdust or lint. Environmental regulations and common sense dictate the removal of the particulate matter from the exhaust stream before it is released into the atmosphere. The particulate matter not only can cause damage to the environment if it is allowed to flow into the atmosphere unchecked, but the particulates, themselves, often have a commercial value which is lost if the air stream carrying the particulate matter is exhausted into the atmosphere.
In the commercial laundry industry, for example, large dryers are utilized. These dryers rely upon the flow of high-temperature air through the laundry tumbler or basket within the dryer to effect the removal of moisture from the laundry. Such a dryer is described in my U.S. Pat. No. 2,643,463 issued June 30, 1953. Because the rate of evaporation of water is proportional to the cube of the velocity of the air moving over the moisture-laden surface, it is essential for maximum efficiency in the drying process to minimize the back-pressure and other factors inhibiting the air flow through the system including the laundry dryer. Numerous types of lint traps are available presently in the laundry industry but they suffer from many limitations. For example, many of these lint traps rely on the use of baffles over which the air flowing from the dryer must pass in order to either be exhausted to the atmosphere or be recirculated. These baffles produce back-pressure in the air circulation system, thus reducing the velocity of the air. Similarly, screens or other forms of filters produced undesirable back-pressure. Additionally, screens and filters require frequent attention to prevent their becoming clogged and completely blocking the flow of air through the system. The cleaning or replacement of the filters may have to be done several times a week which seriously increases labor costs in a commercial laundry operation and, if the filters are disposable, it poses a continuing supply problem for replacement filters. Some of the lint traps having screens require burning of the lint off the screens. This not only causes pollution, which is unacceptable today, but also eliminates the recovery of the lint for commercial uses. For example, the lint which is recovered can be used as a filler in the manufacture of composition roofing shingles.